SERS study on the aggregation mechanisms resulting from the orientation of dipyridinic derivatives on gold nanoparticles.

In this work, was studied the adsorption and orientation of three dipyridinic derivatives 9,10-bis-((E)-2-(pyridin-4-yl)vinyl)anthracene (DPAC), 1,4-bis-((E)-2-(pyridin-4-yl)vinyl)naphthalene (DPNA-T) and 2,6-bis-((E)-2-(pyridin-4-yl)vinyl)naphthalene (DPNA-L) on gold nanoparticles, using Surface Enhanced Raman Scattering (SERS). Systematic modification in the shapes of the bifunctional systems (Cross-shape, T-shape and Linear-shape) shows changes significant in the preferential orientation of these analytes on the nanostructured gold surface. Additional data from UV-vis measurements and TEM images are in agreement with the Reaction Limited Colloid Aggregation (RLCA) mechanisms for DPAC and DPNA-T and Diffusion Limited Colloid Aggregation (DLCA) mechanisms for DPNA-L, showing that for the same analyte concentration, the aggregation mechanism depends on the molecular shape.